Battery monitoring apparatuses that monitor batteries such as lead batteries and lithium ion batteries have been each configured to measure voltages and currents of the battery and to perform various signal processing and the like using the measurement result. In this case, the current is detected on the basis of a terminal voltage of a shunt resistor interposed in series in a path through which the current flows.
In order to suppress a consumption current in a steady state to a low level, the shunt resistor having a comparatively small resistance value is often used. Therefore, the terminal voltage of the shunt resistor is smaller than the voltage of the battery. Accordingly, a dedicated amplifier for amplifying the terminal voltage of the shunt resistor is required for the sensing circuit for sensing the current. In such circumstances, a sensing circuit for sensing the voltage of the battery and a sensing circuit for sensing the current of the battery must be separately provided conventionally, which results in, for example, an increase in circuit scale and an increase in manufacturing cost.
In the configuration described in Patent Literature 1, the same sensing circuit can be used in common for voltage sensing and current sensing by making the capacitance ratio of the capacitor used for the ΔΣ modulator different between the current sensing and the voltage sensing. According to the above configuration, the circuit scale can be reduced.
[Patent Literature 1] JP 5593036 B2